The hornblende root name is in a mineralogical sense as amphiboles in the calcium amphibole subgroup with A(Na+K+2Ca)≤0,5 apfu and 0,5≤Z(Al + Fe3+ +2Ti)≤1,5 apfu. The individual members of the group are defined by it's dominant elements in the Z and W positions

On mindat.org we avoid using variables with the same symbol as elements and deviate from the IMA nomenclaure in that we use X rather than B, Z rather than C and (OH,F,Cl,O) rather than W.

The hornblende root name is an IMA-CNMNC defined amphibole root-name with strict chemical boundaries. it should not be confused with the more loosely defined "hornblende", which is a term used by petrologists and mineral collectors for any black undefined amphibole in the calcium ( and sometimes in the sodium-calcium) subgroups.